Fail safe safing and arming device



United States Patent Inventors Donald A. Brackman Trotwood, Ohio; Robert D. Roland, Richmond, lnd. Appl. No. 720,097 Filed Apr. 10, 1968 Patented Dec. 15, 1970 Assignee Avco Corporation Richmond, !nd., a corporation of Delaware FAIL SAFE SAFING AND ARMING DEVICE Field of Search [56] References Cited UNITED STATES PATENTS 2,789,508 4/1957 Rove et al l02/78X 2,836,118 5/1958 Hjelm l02/78X 2,988,996 6/1961 Junghans et al.. 102/78 3,139,828 7/1964 Delaney et al 102/78 Primary Examiner-Benjamin A, Borchelt Assistant Examiner-Thomas H. Webb Atl0rney-Charles M. Hogan ABSTRACT: The invention is a timing device adapted and arranged to make the nose fuze of a retarded bomb fail-safe in the event of the improper application of forces to the arming system. A verge escapement is utilized incorporating a twospring system acting on the timing block against the escapement, permitting the timing of the motion of the timing block in both directions. The same components which sense and time deceleration forces are used to sense, or limit, the time available from fuze initiation to the application of these forces. If not applied within the time limit, the fuze is dudded.

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PATENTEUDECISISYB 3547;035-

' sum 1 OF 3 :iymnnnmrz CID .V//// ////Ai V V/ /////z INVENTORS. DONALD A. BRACKMAN BY ROBERT D. ROLAND ATTORNEY.

1 PATENTEDBEBI SIS?!) 3.547035 SHEET 2 0F 3 IN VIiNT )RS. DONALD A. BRACKMAN BY ROBERT D. ROLAND W t, W4.

ATTORNEY.

PATENTED JEEI 5 I978 SHEET 3 BF 3 ATTORNEY.

FAIL SAFE SAFING AND ARMING DEVICE The invention relates to timing devices, particularly to timers for use in fuze for retarded bombs which are released from aircraft at low altitudes and designed to arm themselves when sufficient forces of deceleration-induced by high drag fins secured to the bomb body-are generated. This is accomplished by the use of a system of weights which are thrown forwardly in the direction of flight when sufficient deceleration forces are developed.

In the case where for some reason these forces do not develop-as where the drag fins accidentally become separated from the bomb body-it is highly desirable to quickly disarm the bomb so it will not explode. If the bomb is not quickly rendered inoperative under these conditions, danger to the personnel and equipment of thereleasing craft would be created.

Failure of the drag fins to decelerate the bomb body permits the bomb to tumble, whereby random forces are generated which cannot be depended upon to reach a magnitude and to develop in the proper direction to armthe bomb according to the predetermined schedule set up by the fusing mechanism.

According to the invention a timing mechanism is provided which is unaffected by any forces other than those to which the fuze is designed to respond and which will either sense the development of a sufficient magnitude of force, in the proper direction, to permit the fuse to arm, or will sense the failure of such force to develop,-dud the fuse, and thereby insure safe operation for the delivering craft.

In the drawings:

FIG. 1 is a schematic view, with parts cut away, of an inertia-timing sensor constructed in accordance with the principles of the invention with the fuse-actuating mass in its initial position;

FIG. 2 is a similar view with the fuse-actuating mass locked into dud position after sensing the failure of forces of adequate magnitude to develop to cause proper arming;

FIG. 3 is a view similar to FIGS. I and 2 but with the fuseactuating mass fully advanced to permit the fuse to be armed, having responded to the gravitational forces for which it was designed to operate; and

FIG. 4 is a side elevational view of the assembly illustrated in F IG. 1 with adjacent and cooperating parts of ihe fuse (not per se a part of the invention) shown in greater detail.

Referring to FIG. 1, the inertiatiming sensor denoted generally by reference character 9, is mounted for slidable movement on shaft 10 between the ends ofa suitable frame or housing 11, 11, for instance in the nose casing of a retarded bomb. The direction of motion of the bomb trajectory is indicated by the arrow A. An escapement 12 is provided with a conventional pallet 8 and a wheel 13 engaging a rack formed in a timing block 15 at one end ofthe sensor. The timing block 15 is normally held in abutment with an actuating weight 16, hereinafter called a G weight, by tension spring 17 secured to the G weight at 18 and to the timing block 15 at 19. G weight i6 is slidably supported on shaft 10 and held in an intermediate position on said shaft by compression spring 20, abutting the G weight at 22, and the end of the housing at 22.

Only one set of springs is shown in the illustrative embodiment, it being understood that the action of the assembly is rendered more dependable by providing pairs of springs disposed around pairs of shafts.

The construction above described comprises a two-mass system with timing block 15 constituting one mass and G weight 16 the other. These weights are floated between the two limiting surfaces at each end of housing ill. In normal operation of the bomb the drag fins open a fraction of a second after release and impose a high drag on the assembly. When the drag forces exceed approximately four times the force of gravity, the G weight moves forward (downward in FIG. 1) against the resistance of compression spring or springs 20. The timing block 15 stays back, retarded by the effect of engagement with the escapement but it starts being pulled forward against the escapement by the extended connector spring or springs ll7, toward block 16, which at that time is in its fully advanced position.

The escapement 12 which is desirably of the runaway type, is provided with slots 12a mounted on studs IZb adapted to be secured to fixed parts of the housing in order to provide an adjustment for the escapement so it can be set to run in either direction.

immediately upon release of the bomb the only force working against the mass system is that of the'compression springs 20. These start pushing the timing block 15 upward of housing 11 as shown in FIG. 1, moving the escapement mechanism in one direction through wheel 13. The time during which this movement occurs is controlled by the force supplied by the compression springs and the size of the pallet. If no retarding is sensed to overcome the springs, and the mass system moves to a stop (to the extreme position of its travel in the opposite direction to the expected forces of deceleration), it will be locked there by a spring activated pin 25 which moves into slot 26 provided in the timing block. This is shown in FIG. 2.

The time required to dud the bomb is set just longer than the longest expected time for the drag fins to open. Then if the fins fall away without imparting the expected large retardation force, the fuse will be dudded before centrifugal forces build up to cause arming.

If, however, the fins open up within the set time, and retardation is sensed, the G weight will reverse its direction along the axis and the escapement will be actuated in the proper direction to function normally. Retardation will be maintained so that the timing block will be pulled down by the connector springs 17 to the position indicated in FIG, 3, at which time lock pin 27 functions to hold it in arming position.

The mounting of the escapement in slots ll2a adjustment in the balancing of spring rates, travel and pallet size to permit proper timing in both directions.

In practice, the fail-safe-safing and arming device in accordance with the invention is refined and incorporated in the structure as illustrated in FIG. 4, which employs the same reference numerals as FIGS. 1-3. it will be understood that the fuse is enabled to arm when the element 15 reaches the terminal position indicated in phantom lines in FIG. 3. The weight 15 constitutes the arming element and it will be understood that the contents of FIG. 4 to the right of pin 27, con

stitute such prior art and well-known fuse elements or any conventi'onal'fuse construction which is adapted to use a dis-,

placeable element for arming purposes.

Thus it will be seen that the invention, viewed in one aspect,

comprises:

a fail safe safing and arming device for installation in a bomb of the type including fall retarding means comprismg:

a first weight 15;

a second weight 16 which is adapted to respond to deceleration forces caused by fall-retardation to be displaced in the direction of flight;

biasing means 20 for thrusting against said second weight to displace both weights against the direction of flight;

connecting means 17 between the second weight and the first weight whereby the second weight pulls the first weight in the direction of flight during retardation;

a first locking means 25 adapted to restrain the first weight in the event that it reaches its limit of displacement against the direction of flight;

a second locking means 27 adapted to restrain the second weight in the event that it reaches its limit position in the direction of flight; and

a timer 12 which delays the displacement of the first weight,

said timer being operative when retarding does not occur within a time delay after launching to permit the first weight to reach its limit position and to be restrained by the first locking means to prevent arming of the fuse,

said timer being operative upon the development of deceleration forces to permit the first weight to be displaced sufficiently, during a time delay following retardation, that the second weight reaches its limit position and is restrained by the second locking means to arm the fuse,

and means for mounting said weights to permit said displacements.

While there has been shown and described what is at present considered to be the preferred embodiment of the invention, it will be understood by those skilled in the art-that various changes and modifications may be made therein without departing from the scope of the invention as defined in the appended claims.

We claim: g

1. A fail-safe safing and arming device for installation in a bomb of the type including fall retarding means comprising:

a first weight; t

a second weight which is adapted to respond to deceleration forces caused by fall-retardation to be displaced in the direction of flight; biasing means for thrusting against saidsecond weight to displace both weights against the direction of flight;

connecting means between the secondweight and the first weight whereby the second weight pulls the first weight in the direction of flight during retardation;

a first locking means adapted to restrain the first weight in the event that it reaches its limit of displacement against the direction of flight; t

a second locking means adapted. to restrain the second weight in the event that it reaches its limit position in the direction of flight;

a timer which delays the displacement of the first weight;-

said timer being operative when retarding does not occur within a time delay after launching to permit the first weight to reach its limit position and to be restrained by the first locking means to prevent arming of the fuse,

said timer being operative upon the development of deceleration forces to permit the first weight to be displaced sufficiently, during a time delay following retardation, that the second weight reaches its limit position and is restrained by the second locking means to arm the fuse; and i and means for mounting said weights to permit said displacements.

2. A fusing system for a bomb, or the like, comprising:

a first weight movable, from an initial position, towards and away froma terminal arming position in response, respec tively, to a deceleration force of a given magnitude and direction, effective on said system, and an acceleration force of a given magnitude in the opposite direction;

a second movable weight;

first spring means yieldingly urging said weights into a predetermined relative position;

second spring means yieldingly urging said second weight away from said terminal position;

said second weight being free to move subject only to said spring means;

means for limiting the rate of travel of the first weight towards and away from said terminal position; and

means for locking said first weight in a fixed position once it moves a predetermined distance away from said terminal position, whereby a deceleration force of a given magnitude effective on said weights, acting through said first spring means, will move the first member to its terminal position and an acceleration force of a given magnitude and the opposite direction will prevent arming of the bomb.

3. A fusing system as in claim 2 further comprising means for locking said first weight in its terminal position once that position has been reached.

4. A fusing system as in claim 2 further comprising: a frame having means for guiding said weights for sliding movement in a direction aligned with that of the acceleration and deceleration forces and further wherein:

spring disposed in advance of the second weight in the irection of the bombs flight upon release and acting against said frame.

5. A fusing system as in claim 4 further comprising detent means, cooperative with said frame, for locking said first weight in its terminal position once that position has been reached. 

